With more demanding legislation for Internal Combustion (IC) engines more complex valve train assemblies with different valve-lift functions are required. For diesel engines, one of the required functions is an internal Exhaust Gas Recirculation (iEGR). The iEGR function could be achieved with different types of valve train with different complexity and different integration cost. For example, a valve train may include Switchable Rocker Arm. Switchable Rocker Arms with external actuation of latching pins (applied to both or just one exhaust position of each cylinder) can provide full iEGR functionality for standard Type II valve train system with very low integration cost. Such rocker arms may also be used for other functions, such as, for example, Early Exhaust Valve Opening (EEVO), or the like.
Switchable rocker arms for control of valve actuation by alternating between at least two or more modes of operation (e.g. valve-lift modes) are known. Such rocker arms typically involve multiple bodies, such as an inner arm and an outer arm. These bodies are latched together to provide one mode of operation (e.g. a first valve-lift mode) and are unlatched, and hence can pivot with respect to each other, to provide a second mode of operation (e.g. a second valve-lift mode). Typically, a moveable latch pin is used to switch between the two modes of operation.
In some switchable rocker arms the latch pin is actuated internally, that is, it is actuated by a mechanism internal to the valve train assembly of which the rocker arm is part. Although internal actuation mechanisms can save overall space, such internal actuation mechanisms typically require modification of one or more components of the valve train, which can be expensive and complex.